我有一个标签活动，标签包含活动作为内容，并且在标签之间切换时有列表我得到以下内容
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): FATAL EXCEPTION: main
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): java.lang.NullPointerException
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.AbsListView.obtainView(AbsListView.java:1432)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.ListView.makeAndAddView(ListView.java:1745)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.ListView.fillDown(ListView.java:670)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.ListView.fillFromTop(ListView.java:727)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.ListView.layoutChildren(ListView.java:1598)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.AbsListView.onLayout(AbsListView.java:1260)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.widget.FrameLayout.onLayout(FrameLayout.java:338)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.View.layout(View.java:7175)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.ViewRoot.performTraversals(ViewRoot.java:1140)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.os.Handler.dispatchMessage(Handler.java:99)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.os.Looper.loop(Looper.java:130)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at android.app.ActivityThread.main(ActivityThread.java:3683)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at java.lang.reflect.Method.invokeNative(Native Method)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at java.lang.reflect.Method.invoke(Method.java:507)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-21 16:13:24.644: ERROR/AndroidRuntime(2420): at dalvik.system.NativeStart.main(Native Method)
请帮我解决这个问题。